1. Field of the Invention
The present invention relates to a developing member to be incorporated in an apparatus adopting an electrophotographic system, such as a copier, a printer, or a receiving apparatus for a facsimile, for use in contact with or in close proximity to a photosensitive member, and a process cartridge and an electrophotographic apparatus having the developing member.
2. Description of the Related Art
In a copier, a facsimile, a printer or the like using an electrophotographic system, an electrophotographic photosensitive member (hereinafter, also referred to as “photosensitive member”) is charged by a charging unit, and exposed by a laser or the like to form an electrostatic latent image on the photosensitive member. Then, a toner in a developing container is applied on a developing member by a toner supplying roller and a toner regulating member, and the electrostatic latent image on the photosensitive member is developed by the toner on a contact portion between the photosensitive member and the developing member, or in close proximity of the contact portion. Thereafter, the toner on the photosensitive member is transferred by a transfer unit to recording paper and fixed by heat and pressure, and the toner remaining on the photosensitive member is removed by a cleaning blade.
In an image forming apparatus with a non-magnetic one-component contact developing system, a conductive electrophotographic member having an electric resistance of 103 to 1010 Ω·cm is generally used for a developing member.
In recent years, performances required for a developing member for use in an apparatus adopting an electrophotographic system have been made higher, and a developing member such as a developing roller having two layers, in which a surface layer is provided on the surface of an elastic layer, has been often used from the viewpoints of high image property and high durability.
For the surface layer in the developing member, a urethane resin excellent in wear resistance and charge-imparting property to a toner is widely used. In recent years, an improved technique of the surface layer has also been proposed in order that the function of a charging member may be further enhanced. Japanese Patent Application Laid-Open No. 2004-339253 discloses that a urethane resin is allowed to contain an acrylic resin to enhance wear resistance and slidability. In addition, Japanese Patent Application Laid-Open No. 2008-139482 discloses that a polyether-based urethane resin is allowed to contain an acrylic resin having predetermined physical properties to suppress toner adhesion under a high-temperature and high-humidity environment.